Cyclic o,o,s-triesters of phosphorodithioic acid

ABSTRACT

Cyclic O,O,S-Triesters of phosphorodithioic acid are excellent accelerators of sulfur vulcanization at elevated temperatures, thereby making possible a considerable reduction in the cure time. Additionally, certain novel compounds of the above class and their preparation are disclosed.

United States Patent 91 Nudenberg et al.

[ CYCLIC 0,0,S-TR1ESTERS OF PHOSPHORODITHIOIC ACID [75] Inventors:Walter Nudenberg, Newtown,

Conn.; Merlin P. Harvey, Denison. Iowa; James Urquhart Mann,

Wayne, NJ.

[73] Assignee: Uniroyal, Inc., New York, N.Y.

[22] Filed: July 17, 1974 21 Appl. No.: 489,220

Related US. Application Data [62] Division of Ser. No. 282,640, Aug. 21,1972, which is a division of Ser. No. 66,870, Aug. 25, 1970, Pat. No.3,712,878.

[52] US. Cl 260/927 R [Sl] Int. Cl C07d 105/04 [451 July 22, 1975 [58]Field of Search 260/927 R [56] References Cited UNITED STATES PATENTS2,859,086 1l/l958 Feild, Jr. et a1. 260/927 R X Primary Examiner-AntonH. Sutto Attorney, Agent, or Firm-Robert J. Patterson, Esq.

[57] ABSTRACT 3 Claims, No Drawings CROSS-REFERENCESTO RELATEDAPPLICATIONS This application is'a division of our copending applicationSer. No. 282,640g'filed Aug, 21, 1972 which in turn is a division of ourcopending application Ser. No, 66,870, filed Aug. 25, I970, issued onJan. 23, 1973 as US. Pat. No. 3,712,878.

This invention relates to (l) the use of 0,0,8- triesters ofphosphorodithioic acid to accelerate the sulfur vulcanization of rubberyelastomers at elevated temperatures (i.e., at approximately 400F andhigher), (2) vulcanizable compositions containing such triesters, (3)improved cured vulcanizates produced in ac cbrdance with the foregoinguse-and (4) many of the triesters themselves as novel compounds,

The 0,0,S-triesters of phosphorodithioic acid that are within theinvention are the addition products, or adducts, resulting from theaddition of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid(hereinafter referred to as DTP for convenience) or homologues across anunsaturated bond, such as, for example I i.

C C as in styrene or alkene;- -C C as in 'phenylac'etylene or acetylene;C N as in acetoxime;- I

as in benzalazine; and C E N, as in acetonitrile: t i

The compound to which DTP or its homologues add can have more than oneunsaturated bond, and the additive reaction may occur at one or more ofsuch bonds. n L- The structural formula DTP is:

Accordingly, the generalized structure of the adduct can be representedas follows:

. wherein R and R are alkyl groups which can be the represents theoptional presence of an oxygen atom, and R is the after-addition moietyof thereactant to which DTP has been added. The R moiety can be alkylexcept methyl, alkenyl, alkynyl, aralkyl except benzyl andalkyl-substituted aralkyl except alkyl substituted benzyl, an alicycli'cradical (including polycyclic radicals) and the alkyl substitutedderivatives thereof, and a heterocyclic radical containing one or moreheteroatoms selected from sulfur, oxygen and=nitrogen. R can alsobe OCH2R4 to give bis-disters which are made by reacting two moles of DTP orits homologues with alcoholic iodine. in which case the optional oxygenis not present. R and R may have the same values as R and RAdditionally, the R moiety can contain any of the following functionalsubstituent groups:

When R is an aliphatic compound or contains an aliphatic moiety(for'i'nstance when R is an alkyl or an alkyl substituted .alicyclicradical), such aliphatic compound or moiety can have from I to 10 carbonatoms, preferably from I to 5. Examples of R radicals containing bothnon-functional and functional moieties follow.

Examples of R as a monovalentgfadical.(i.e.,, x=l) are:

2-3-dimethyltetramethy1ene (14) -Cl-l C1-l CONHCl-l CH Cl-lethylenecarbonyliminotrimethylene -C1-l CH C1-l OCH Cl-1 CHoxybis(trimethy1ene) 2,S-dimethylhexamethylene Additional representativeexamples of R are ethyl. propyl, butyl, vinyl, allyl, isopropenyl,butenyl, pente nyl, butynyl, pentynyl, phenethyl, phenylpropyl,phenylbutyl, phenylpentyl, naphthylmethyl, naphthylethyl,naphthylpropyl, naphthylbutyl, naphthylpentyl, cyclopropyl, eyclobutyl,cyclopentyl, cyclohexyl, decahydronaphthyl.

Representative examples of heterocyclic radicals containing one or moreheteroatoms selected from sulfur, oxygen and nitrogen aredihydrothienyl, tetrahydrothienyl, 2,3-dihydrobcnzothieny1,dihydrofuryl, dihydropyranyl, chromanyl, pyrrolinyl, piperidyl,indolinyl, indolidinyl, 1,3-dithio1anyl, 1,4-dioxany1, imidazolinyl,imidazolidinyl, pyrazolidinyl, pyrazolinyl, dihydropyrazinyl,piperazinyl, dihydropyrimidinyl, dihydropyridazinyl, benzimidazolinyl,1,2-dihydrobenzotriazolyl, dihydroquinolyl, 1,2-dihydroquinoxa1inyl,dihydrooxathiinyl, thiazolinyl, isothiazolidinyl, dihydrobenzothiazolyl,oxazolidinyl, isoxazolidinyl, oxazolinyl, isoxazolinyl, dihydroxazinyl,2-benzoxazoliny1, oxadiazolidinyl, oxathiazolinyl.

Representative examples of alkyl substituted homologues of theaforementioned radicals are methylpropyl, methylbutyl, methylpentyl,ethylpropyl, ethylbutyl, ethylpentyl, 1,1,3 ,3-tetramethylbutyl4,4-dimethylhexyl, methylbutenyl, methylbutynyl, methylpentynyl,a-methylbenzyl, a-ethylbenzyl, a-propylbem zyl, a-butylbenzyl,methylphenethyl, ethylphenethyl, propylphenethyl, butylphenethyl,a-methylnaphthyL methyl, ethylnaphthylpropyl propylnaphthylbutyl,methylcyclohexyl, ethylcyclopropyl, propylcyclobutyl,methylphenycyclohexyl, ethyltetrahydronaphthyl, butyltetrahydronaphthyl.

Representative examples of alkyl substituted hetero cyclic radicals arephenethyldihydrothienyl, methylbenzodihydrothienyl, propyldihydrofuryl,butyldihydropyranyl, isopropylchromanyl, butylpyrroinyl, ethylpiperidyl,ethylindolinyl, isopropylindolinyl, methyl-1,3-dithiolanyl,ethyltetrahydrothienyl, propyl- 1,4-dithianyl, butyl-1,3-dioxo1any1,methyl-1,4- dioxanyl, ethylimidazolinyl, propylimidazolidinyl,butylpyrazolidinyl, pentylpyrazolinyl, methylpiperazinyl,ethyldihydropyrimidinyl, propyldihydropyridazinyl,methyl-2,3-dihydrobenzimidazolyl, ethyltetrahydroquinolyl,propyltetrahydroquinolyl, propyldihydroquinoxalinyl,methyldihydrooxathiinyl, ethylthiazolinyl, propylisothiazolinyl,methyldihydrobenzothiazolyl, butyloxazolidinyl, pentylisoxazolidinyl,methyloxazolinyl, ethylisoxazolinyl, propyldihydrooxazinyl,methyldihydrobenzoxazolyl, propyloxadiazolinyl, butyloxathiazolinyl.

Of the 0,0,S-triesters of phosphorodithioic acid which fall within theabove general formula, many have been previously reported in theliterature. .1. H. Bartlett (U.S. Pat. No. 3,159,664) discloses, forinstance, cyclic 0,0-2,2-dimethyltrimethy1ene S-a-methylbenzylphosphorodithioate and its method of preparation; and the compoundbis(cyclic 0,0,-2,Z-dimethyltrimethylene) dithiobis(phosphorothioate)has been reported by R. S. Edmundson in Tetrahedron, vol. 21, pp.2.3792.387. (1965). It should be understood, however, that these twocompounds have not been previously described as accelerating agentswithin or without the temperature limits of the invention. Althoughsynergistic combinations of thiazole accelerators and zincphosphorodithioate 0,0-diesters are known (see US. Pat. No. 3,308,103 toCoran), it will be hereinafter shown that such compounds are inferioraccelerating agents compared with the compounds of the invention at theele vated curing temperatures of the inventive technique.

A new type of adduct disclosed herein is the result of the addition ofDTP and its homologues to a C=N grouping. This is a new reactionpreviously unreported. This type of adduct is exemplified by cyclic0,0-2,2- dimethyltrimethylene S[ a-( benzylidenehydrazino benzyl]phosphorodithioate whose preparation is described in Example 7 below.

PREPARATION The following examples illustrate the preparation of variousadducts that are within the invention.

EXAMPLE 1 This example illustrates the preparation of cyclic0,0-2,Z-dimethyltrimethylene S-a-methylbenzyl phos phorodithioate whichis the Markovnikoff 1:1 mole ad' dition product of cyclic0,0-2,Z-dimethyltrimcthylene phosphorodithioic acid and styrene.

10.4 g. (0.1 mole) of peroxide-free styrene was added dropwise duringfive minutes to a continuously stirred solution of 19.8 g. (0.1 mole) ofcyclic 0,0-2,2- dimethyltrimethylene phosphorodithioic acid in 200 m1.of reagent benzene at room temperature. The mix ture was then stirredand refluxed for nine hours. Evaporation of the solvent gave a liquidwhich crystallized very slowly. Recrystallization from cyclohexane gavea solid having amelting point of 84-85.5C. The yield of recrystallizedproduct was 9.5 g. (31.5% of theory).

Analysis for C H O PS Cald. C, 51.64; H, 6.33; P, 10.24; S, 21.21.Found. C, 51.45; H, 6.28; P, 10.01; S, 20.34.

The preparation of this particular adduct has been reported in theliterature (U.S. Pat. No. 3,159,664 to J. H. Bartlett).

EXAMPLE 2 This example illustrates the preparation of the anti-Markovnikoff 1:1 mole addition product of cyclic0,0-2,Z-dimethyltrimethylene phosphorodithioic acid and styrene.

A mixture of 20.8 g. (0.2 mole) of commercial grade styrene, 39.6 g.(0.2 mole) of cyclic 0,0-2,2- dimethyltrimethylene phosphorodithioicacid in 100 ml. of reagent benzene and 0.697 g. (0.004 mole) oftertbutyl peroxypivalate (a solution in mineral spirits) was stirred andheated at 45C for 20 minutes and then was heated to reflux. Refluxingand stirring were continued for 7 hours. A 2 ml. portion of the reactionsolution was evaporated to dryness and the residue afterrecrystallization from Skellysolve melted at 67-7lC. A secondrecrystallization from Skellysolve raised the melting point to 7275C. Athird recrystallization from Skellysolve raised the melting point to75.577C. A fourth recrystallization from Skellysolve raised the meltingpoint to 7677.5C. A mixed melting point with cyclic0.0-2,2-dimethyltrimethylene phosphorodithioic acid was 5259.5C. Themixed melting point with a purified sample (melting point 8485.5C) ofthe product of Example 1 (the Markov' nikoff 1:1 adduct) was 57-62C.

Analysis for C H O PS: Calcd. C, 51.64; H, 6.33; P, 10.24; Mol. wt=302.4. Found. C, 51.63; H, 6.37; P, 10.36; Mol. wt 303.0.

These mixed melting points and analyses indicate that the product wasneither the recovered dithioic acid nor the product from Example 1, butwas the anti- Markovnikoff 1:1 mole addition product, viz., cyclic0,0-2,2-dimethyltrimethylene S-phenethyl phosphorodithioate.

EXAMPLE 3 This example illustrates the preparation of cyclic0,0-2,2-dimethyltrimethylene S-[1,2,3a,4,7,7ahexahydro-4,7-methanoinden-2-yl] phosphorodithioate. whichis the 1:1 mole adduct of dicyclopentadiene(3a,4,7,7a-tetrahydro'4,7-methanoindene) and cyclic0,0-2,Z-dimethyltrimethylene phosphorodithioic acid (DTP).

39.6 g. (0.2 mole) of cyclic 0,0-2,2- dimethyltrimethylenephosphorodithioic acid was dissolved at room temperature in 200 ml. ofdry toluene contained in a 500 ml.. 3-neck, round bottom flask equippedwith a stirrer, thermometer, reflux condenser and dropping funnel. Tothe resultant solution, while stirring continuously,-was added 25.4 g.(0.2 mole) of dicyclopentadiene through the dropping funnel during aperiod of minutes. The ensuing exothermic reaction raised thetemperature of the reaction mixture to about 529C. in 10 minutes, thesolution remaining colorless. After 24 hours at room temperature, thesolution was placed in a beaker on a warm steam bath. As the solvent(toluene) evaporated, a white solid crystallized from solution. After 24hours, the mixture was filtered to remove the white, solid product whichweighed 54.6 g. After recrystallization from Skellysolve and airdrying,the melting point of the product was 1 l3-l 16C. A secondrecrystallization from Skellysolve gave a product with a melting pointof ll3.5-l15.5C.

Analysis for C H O PS (1:1 mole adduct): Cald. C, 54.52; H, 7.02; P,9.37; S, 19.41. Found. C, 53.83; H, 6.82; P, 8.89; S, 18.08.

An infrared spectrum of the above 1:1 mole adduct showed the completeabsence of absorption at 1.610 cm, which is characteristic of the doublebond between carbon atoms 2 and 3 in the following formula:

An absorption maximum was present, however, at 1,575 cm, which ischaracteristic of the double bond between carbon atoms 5 and 6,indicating that the DTP had added across the double bond between carbonatoms 2 and 3.

EXAMPLE 4 This example illustrates the preparation of cyclic0,0-2,2-dimethyltrimethylene S,S-(bicyclo[2.2. l- ]heptane-2,5-diyl)phosphorodithioate, which is the 1:2 mole adduct of norbornadiene(bicyclo[2.2.l]2,5- heptadiene) and cyclic 0,0-2,2-dimethyltrimethylenephosphorodithioic acid.

9.2 g. (0.1 mole) norbornadiene was added dropwise during 6-7 minutes toa continuously stirred solution of 39.6 g. (0.2 mole) cyclic 0,0-2,2-dimethyltrimethylene phosphorodithioic acid in 150 ml. of reagentbenzene at room temperature. An exothermic reaction caused thetemperature of the mixture to rise to 585C. When the temperature haddropped to 40C., product began to crystallize from the reaction mixture.Filtration of the mixture gave 39.0 g. of product (79.9% of theory). Themelting point (l84l94C.) of the crude product was raised to l94-l95C. byrecrystallization from hot cyclohexane.

Analysis for C H O P- S (1:2 mole adduct): Cald. C, 41.79; H, 6.19; P,12.68; mol. wt., 488.6. Found. C, 41.28; H, 5.89; P, 12.74; mol. wt.,459.0.

EXAMPLE 5 This example illustrates the preparation of cyclic0,0-2,Z-dimethyltrimethylene S-l-methylheptyl phosphorodithioate, whichis the adduct of l-octene and cyclic 0,0-2,2-dimethyltrimethylenephosphorodithioic acid.

11.2 g. (0.1 mole) of l-octene was added to 19.8 g. (0.1 mole) of cyclic0,0-2,Z-dimethyltrimethylene phosphorodithioic acid at room temperature.An exothermic reaction did not occur. After heating the reaction mixtureat C. for 8 hours, it was placed under reduced pressure (2535 mm.) at atemperature of 75-85C. on a rotary evaporator for two hours. Theresidual, viscous liquid weighed 30.3 g. (98% of theory).

Analysis for C H- o- PS z Cald. C, 50.29; H, 8.76; P, 9.97; S, 20.66.Found. C, 49.92; H, 8.64; P, 9.84; S, 20.0.

EXAMPLE 6 This example illustrates the preparation of cyclic0.0-2,Z-dimethyltrimethylene S,S'-[2,2-(1,3- phenylene)diisopropyl]phosphorodithioate, which is the adduct of 2 moles of cyclic 0,0-2,2-dimethyltrimethylene phosphorodithioic acid and one mole ofm-diisopropenylbenzene.

15.8 g. (0.1 mole) of m-diisopropenylbenzene, which had been purified bypassage through chromatographic alumina, was added dropwise whilestirring for six minutes to a solution of 39.6 g. (0.2 mole) of cyclic0,0-2,2-dimethyltrimethylene phosphorodithioic acid in ml. of reagentbenzene at room temperature. A slightly exothermic reaction caused anelevation of 5C. in the temperature of the reaction mixture. AfterSkellysolve and chloroform gave a product melting at' Analysis for C I-103 5 121 mole adduct: Calcd. C, 47.62; H, 6.54; P, 11.17; S, 23.12; mol.

wt..554.7. Found: %C.47.32; H.632; P. 11.18;

% S, 25.60; mol. wt., 582.0.

' EXAMPLE 7 This example illustrates the novel preparation of cyclic0,0-2,2-dimethyltrimethylene S-[a-(benzylidenehydrazino)benzyl]phosphorodithioate, which is the adduct of one mole of cyclic 0,0-2,2-dimethyltrimethylene phosphorodithioic acid to one mole of1,2-di(benzylidene)hydrazine. l,2-di(benzylidene)hydrazine itself is thecondensation product-of 2 moles of benzaldehyde and one mole ofhydrazine.

To a solution of 39.6 g. (0.2 mole) of cyclic 0,0-2,2-dimethyltrimethylene phosphorodithioic acid in 150 ml. of reagentbenzene was added, dropwise, with continuous stirring over a period offive (5) minutes at 25C., a solution of 20.8 g. (0.1 mole) ofl,2-di(ben-' zylidene)hydrazine. (.benzylidene)hydrazine. The resultantmild exothermic reaction caused the temperature of the mixture to rise5C. and within minutes a yellow precipitate began to form. Stirring wasdiscontinued after a total of two and one-half hours, after which themixture was filtered to isolate the yellow product which had a meltingpoint of l.,3l.5135.5C. Recrystallization of the yellow'product from amixture of one liter of cyclohexane and.0.5 liter of benzene gave 28.3g. of product melting at l32l35C. A second recrystallization raised themelting point to 135-136C.

Analysis for C l-l N O PS (1:1 mole adduct): Calcd. C, 56.14; %'H, 5.70;P, 7.62; S, 15.78. Found. C, 54.81;% H,-5.7 8; P, 7.77; S, 15.33.

The elemental analysis indicated that the product obtained was a 1:1molar addition product of the phosphorodithioic acid and the azine. Theyield of product before recrystallization was 37.3 g. or 91.9% oftheory.

EXAMPLES This example illustrates the preparation of cyclic0,0-2,2-dimethyltrimethylene S-(oxo)-ahydroxyphenethylphosphorodithioate. This is the 1:1:1 mole adduct of cyclic 0,0-2,2-dimethyltrimethylene phosphorodithioic acid, styrene and oxygen.

placed quickly into the oxygenator and forty pounds of 1 oxygen pressurefrom an oxygen cylinder was applied while shaking the reactants. Within2 hours, a mild exothermic reaction occurred during the uptake of'0.l29

moles of oxygen. The reaction mixture was cooled to room temperature.The solid product, weighting only,

215 'grar'nsafterdrying, was filtered off. The reaction mixture filtratewas diluted with 145 ml. of toluene, washed with two (2) 100 ml.portions of 8% aqueous sodium bicarbo'nate solution, one (1) 100 ml.portion of water, then freed of solvent and dried under reduced pressure(2 mm. at C. for two hours). The weight of the very viscous,amber-colored, taffy-like residue was 37 g. (55.3% of-theory).

Analysis for C l-l O PS Cald. C, 46.69; H,

5.73; P, 9.26. Found. C. 48.41: H. 5.62; P.

An infrared spectrum of the chemical,

(C H O PS showed absorption maxima at: (1) 3,450 cm (presence of OHgroup); (2) 685 cm? (presence of P=S grouping); (3) 1,050 cm and 990 cm(presence of P-O-C grouping).

The reaction of the previous example is not unique. Thus the addition ofDTP according to the disclosure in the presence of oxygen under pressureresults in the S-(oxo)-a-hydroxy-form of the resultant compound. Forexample, in the case of Example 5, 0,0-2,2-

dimethyltrimethylene S-(oxo)-2-hydroxy-n-octyl phosphorodithioate; andin the case of Example 10, lauryl 3-[cyclic 0,0-2,2-dimethyltrimethylenephosphorodithioyl-(S-oxo)l-2-hydroxypropionate.

EXAMPLE 9 This example illustrates the preparation of bis(cyclic0,0-2,2-dimethyltrimethylene) dithiobis(phosphorothioate);

"To a solution of 39.6 g. (0.2 mole) of cyclic 0.0-2,2-

dimethyltrimethylene phosphorodithioic acid in 200 ml. of absolutemethanol was added a solution of 25.4 g. (0.2 atomic weight) of iodinein 200 ml. of absolute ethanol at 25C. in one portion with continuousstirring. Th reaction mixture was stirred continuously for 48 hours,after which a solid product was isolated by filtration, washed with asmall amount of absolute ethanol, and then air-dried. Recrystallizationfrom ethanol solution yielded 9.1 gms. (23% of theory) of a white solidwith a melting point of 135137C.

Analysis for C H O P S Cald. C, 30.45; H, 5.11; P, 15.70. Found. C,30.77; H, 5.24; P,

The preparation of this particular product has been reported in theliterature (Tetrahedron, vol. 21, pp.

EXAMPLE 10 This example illustrates the preparation of lauryl 2- (cyclic0,0-2,Z-dimethyltrimethylene phosphorodithioyl) propionate, which is the1:1 mole adduct of cyclic 0,0-2,2-dimethyltrimethylene phosphorodithioicacid to lauryl acrylate.

To a solution of 19.9 g. (0.1 mole) of cyclic 0,0-2,2-dimethyltrimethylene phosphorodithioic acid in 70 ml. of methylenechloride was added 24 g. (0.1 mole) of lauryl acrylate in small portionsover a period of about one-half hour. The reaction mixture was thenrefluxed for two and one-quarter hours and then washed successively with50 ml. of saturated, aqueous sodium bicarbonate solution and 100 ml. ofdistilled water. The

' 'washed solution was then treated with Darco (activated charcoal),filtered and evaporated. The residual'liquid was placed under reducedpressure (3 mm.) for five hours at C. The weight of the clear viscousliquid was 36.2 g. (yield 82.4% of theory, calculated as the 1 1 12 1:]mole adduct). An infrared spectrum showed the F Qy li Qf() 2 2 dithyltrip qthylr n absence of the vinyl unsaturation characteristic ofthe hy mi' P P P Q J 1 I I l t G Cyclic 0.0-2.2 dimcthyltrimethylcnc SSy fy X r [2 2'-(1.3-phenylenc)diisoprcn'iyll phos- Analysis for C H O PSCald. C, 54.77; H. phorodithioate S c H Cyclic0.0-2.2-dimethylti'imethylene -la- P Found C H-885 P 5(bcnzylidcnchydrazino)b cnzylI phosphorodithioatc The elemental analysesshowed that the chemical was I 'L c the 1:1 mole a du t as indicatedabove J Bis(cyclic 0.0-2.Z-dimcthyltrimethylenc)' dithiobis(phosphorothioatcl I Use Of the Triesters 21S Accelerators m K LuurylZ-(cyclic 0.0-2.2-dimcthyltrimcthylcne- I phosphorodithioyl)propionateIn the process of vulcanizing rubbers, it Is desirable to accelerate thevulcanization rate so that the production efficiency of a given sizevulcanization unit can be The compound formula (Base Formulation) usedin increased. One approach to this result has been to raise thisevaluation was: the vulcanization temperature, but the resulting vull5canizates have shown themselves to be of inferior quality in severalrespects. The present compounds, on the Pans by we'gm other hand, arevery good co-accelerators of the sulfur Royalcne 1000 vulcanizationprocess at elevated temperatures (i.e., at H AF blacvk H 50.0 leastabout 350 to 400F) when used in combination 20 g 'g zgg 2:8 with suchprimary accelerators as the thiuram sulfides gte zfiric acid I t u urand disulfides, the dithiocarbamates and the thiazoles.zMercapmbenzmhiazolc 0.5 It thus becomes possible to shorten the curetime very I83 0 substantially. For example a 30 minute cure at 320F. canbe shortened KO jUSt 5 minutes at 400F. I Anethylenc-propylene-dicyclopentadiene terpolymer (EPDM) having an iodinenxfiihcr of Is). an itga'lene-pmpylene ratio of 60-40 and a Mooneyviscosity .-4 at 2l F.) o r 1 l ZIA pn l j yg gi a gegif: glravity0.9272. Saybolt viscosity at 210F. This example demonstrates the use ofthe chemicals Sewn Mr mmc of the invention. Normally they function asaccelera- Two known prior art accelerators appear as comtors andgenerally can be used with any conventional accelerator e a thiazole adithiocarbamate a thiupounds A and B A is Monex (tetramethylthlj urammonosulfide) and 8" is a zinc diester of hosram monosulfide a thiuramdisulfide or a sulfenamide p t 1 t phorodithioic acid [zinc0,0-b1s(4-methyl-2-pentyl) ype acce em phosphorodithioate]. Theparticular zinc phosphorodithioate used for comparison purposes is onewhich in combination with MBT gives a synergistic effect when CodiChemical Name used to accelerate the sulfur vulcanization ofethylenepropylene terpolymers using-a thiazole-type accelera- Qgetragigtgyltlgiuram mgnosulfidc (01' (US. Pat. N0. 3,308,)?! t0 Coran).Chemicals C lf pmspmw to K are the nine chemicals whose preparation isgiven C Cyclic 0.0-2.2-dimethyltrimethylcne S-ain the above examples l,and 3-10, inclusive. Two difmcthylbenzyl phosphorodithioalc o D Cyclic0mhfimmymimehylenc Ll ferent cures, V12. (1) a 30 minute cure at 320 F.,and 3a' 4 7 7 h hyd 4 7 th i d z (2) a 5 minute cure at 400 F., wereused. Stress-strain yl] phosphorodithioatc data, includin Sb 1' A ECyclic 0.0-2.2dimcthyltrimethylene s.s'- 4s g a hardness l obtamed(bicycmzll lhcpmneajdiyl) phw on test pieces which has been vulcanizedin a press at phorodithioatc the two different temperatures indicatedvTable I 7 Stock 1 2 3 4 5 6 7 8 9 10 ll l2 [3" Base Formulation 183 I83183 183 I83 l83 183 183 183 I83 I83 183 l82.5

Chemical K i 5 1 I v 30 Property For 30 Minute Cure-at 32OF.

Shore A 59 5s '47 52 "152 47 v 57 56 i 52 53 34 47 46 (1)Tensi1e, PS!3210 3350' i 840 '1730 820- 940' 2800- 3230 11.70 2880 245 1040 500(2)E1on 510 570 I070 900 1000 980; .,640 640 1000 690 1140 950 1000(3)S-390,p5l 1170 915 210 325 210 215 ,700 710 245 575 225 2 l 'l 1Property 1.

For 5 ;Minute Cure at 400F.

Table I -Continued Stock 1 2 3 4 5 6 v x I 9 "10 1 i1 12 13* Shore A 56I 49 52 53 55 51 55 57 55 51 42 Tensile. psi 3220 1870 Z760 Z660 26202560 2850 2820 3190 2100 1750 Elongation. 7: 620 790 780 720 750 790 610750 590 510 810 S-300. psi 82.0 405 525 525 455 465 735 805 525 690 260Bloom* 3 4 l l l l 2 2 2 l 1 After one (1) week at room temperature: 1none; 2 very slight; 3 moderate: 4 heavy (I Tensile strength at break(2) Ultimate elongation (3) Modulus of elasticity at 300%. elongationBase formulation without 0.5 pt of MBT The results given in Table 1 showthat the chemicals of the invention acting as co-accelerators give goodhigh temperature (e.g. 400F.) sulfur cures; substantially equivalent tothe cures obtainable with prior art accelerators such as the thiuramsulfides and the zinc diesters of phosphorodithioic acid. The comparisonof the high temperature (400F.) cure with the standard temperature(320F.)cure shows incipient reversion in the Monex stock (A) andappreciable reversion of the zinc diester stock (B). Stocks C to J showthat adequate physical properties were developed after only 5 minutes at400F. with no evidence of reversion. It is obvious that satisfactorycures can be obtained at temperatures between 320F. and 400F. and aboveby proper adjustment of the cure time. An outstanding characteristic ofthe chemicals of this invention is that unlike the prior artaccelerators they produce vulcanizates with very little or no bloom,thereby making them especially useful in injection molding formulations.

The accelerators of the invention can be used to accelerate the sulfurvulcanization of both low and high unsaturation rubbers.

Examples of low unsaturation rubbers are: (1) the EPDM rubbers preparedby interpolymerizing a monomeric mixture containing ethylene, a higheralpha monoolefin containing 3-16 carbon atoms and a polyene having twoor more carbon-to-carbon double bonds. The preferred polyenes includedicyclopentadiene, 1,4-hexadiene, 1,3-pentadiene, cyclooctadiene,cyclooctatetraene, tridecadiene, 5-methylene-2- norbornene,5-ethylidene-2-norbornene, 5-a-propylidene-2-norbornene,S-isopropylidene-Z- norbornene, 5-n-butylidene-2-norbornene,

5-isobutylidene-Z-norbornene, 5-(2-methyl-2- butenyl)-2-norbornene,5-(3-methyl-2- butenyl)norbornene and 5-(3,5-dimethyl-4-hexenyl)-2-norbornene; (2) the butyl rubbers which are copolymers of about 95 to99 parts of isobutylene and correspondingly 5 to 1 parts of isoprene,the solution polymerization being effected at low temperature in thepresence of a Friedel-Crafts polymerization catalyst of the type ofaluminum chloride or boron trifluoride.

Examples of high unsaturation rubbers include natural rubber, syntheticrubbers, and mixtures thereof.

The synthetic rubbers may be the products of the polymerization ofvarious monomers. Such synthetic rubbers are: (l) polymers of butadienessuch as 1,3- butadiene, 2-methyl-1,3-butadiene(isoprene), 2- chloro-l,3-butadiene (chloroprene), 2,3-dimethyl-l,3- butadiene piperylene, l(or 2)-phenyl-l,3butadiene and copolymers of mixtures thereof; and (2)copolymers of mixtures of one or more of such 1,3-butadienes with up to70% of such mixtures of one or more monoethylenic monomers which containa Cl-l ==c group.

Examples of such monoethylenic monomers include aryl olefins such asstyrene, vinylnaphthalene, a-methylstyrene, p-chlorostyrene, the amethyIene-carboXylic acids and their esters, nitriles, and amides, suchas acrylic acid, methyl acrylate, methyl methacrylate, acrylonitrile,methacrylonitrile, methacrylamide; methyl vinyl ether; methyl vinylketone; vinylidene chloride; vinylpyridines such as 2-vinylpyridine,Z-methyl-S- vinylpyridine; vinylcarbazole. Commercial synthetic rubbersof this type, made by aqueous emulsion polymerization with a peroxidecatalyst, are SBR (copolymer of butadiene and styrene) and NBR(copolymer of butadiene and acrylonitrile). Some of these rubbers may beprepared by the solution polymerization of: 1 1,3-butadiene using ascatalyst the reaction product of aluminum trialkyl and titaniumtetrachloride or (2) 2- methyl-l,3-butadiene(isoprene), using ascatalyst the reaction product of aluminum trialkyl and titaniumtetrachloride.

EXAMPLE 12 Results similar to those of example 11 are obtained when,isoprene (synthetic or natural), styrenebutadiene (SBR) andacrylonitrile-butadiene (NBR)'rubbers are used in the inventivetechniques.

The inventive accelerators are particularly useful in the production ofvulcanized rubber articles reinforced with polyester (linearterephthalate polyester) fibers such as those described by Daniels inU.S. Pat. No. 3,051,212 and Chantry in U.S. Pat. No. 3,216,187. Theserubber articles include pneumatic tires, V-belts, flat belts, Timingbelts (toothed power or synchronizing belts),footwear. coated fabrics.rubberizedfabric containers, etc. When these articles are made using arubber vulcanizing system with the so-called delayed action acceleratorssuch as the thiurams or the sulfenamides, it has been found that theseaccelerators exert a deleterious effect on the polyester fiberreinforcement. This deleterious effect is accentuated when the articleis subjected to elevated temperatures in service, such elevatedtemperatures arising from environmental heat and/or internal heatgenerated by repeated flexure as in the case of a pneumatic tire or abelt. Ap parently these accelerators during the cure and/or in serviceform a basic environment which accelerates hydrolytic and/or chainscission of the polyester molecules which in turn causes degradation inthe physical properties of the composite article.

The inventive accelerators are uniquely suited as coaccelerators insulfur vulcanizing systems using thiuram or sulfenamide acceleratorsbecause at the elevated curing temperatures of about 400F. they generateacidic products which can counteract the basic products of the thiuramor sulfenamide accelerators. This counteraction by the inventiveaccelerators results in a less basic environment which in turn greatlyreduces the degradation of the polyester fiber reinforcement.

Typical sulfur-containing vulcanizing agents which are examplary of thevulcanizing agents to be used in the inventive technique are:

Vulcanizing Agent parts/ parts rubber Sulfur l. Tuex (tetramcthylthiuram2.0 disulfide) Ethyl Tuex (tctraethylthiuram disulfidc) Vultac (alkylphenol disulfidcs) Sulfasan R (4.4-dithiodimor' pholinc) It should beunderstood that the particular sulfurcontaining vulcanizing agentselected and the amount thereof used for vulcanization is not criticalto the practice of the inventive technique; the type and quantity ofvulcanizing agent used need only be that as would effect vulcanizationunder ordinary prior art conditions.

Typical prior art accelerators with which the inventive accelerators canbe used are, in addition to MBT and MBTS:

In general, the weight ratio of the inventive accelerator to the priorart accelerator is from 1:] to :1, with about 2:1 preferred. The rubbercompositions which can be cured with the inventive accelerators cancontain the usual added additional ingredients, such as sulfur,pigments. antioxidants and/or antiozonants, fillers, extenders, etc.Curing temperatures can range from about 400F. up to the highestpermissible temperature depending upon such well-understood factors asthe time of cure, and the type of rubber, prior art accelerator.activator, etc., used.

Of course, it is readily apparent to those skilled in the art, thatthere are variations of the invention which can be made withoutdeparting from its scope and spirit, and all such variations whichbasically rely on the teachings disclosed herein are considered to bewithin the scope of the foregoing description and appended claims.

Having thus described our invention, what we claim and desire to protectby Letters Patent is:

l. A compound having the formula:

wherein R, and R are C to C alkyl groups which can be the same ordifferent; the 6 portion represents the optional presence of an oxygenatom; and R is 2,5- norbornylene.

2. A compound having the formula:

wherein R and R are C, to C alkyl groups which can be the same ordifferent; and R is 2,5-norbornylene.

3. The compound cyclic 0,0-2,2- dimethyltrimethylene S,S-(bicyclo[2.2.l]heptane-2,5- diyl) phosphorodithioate.

1. A COMPOUND HAVING THE FORMULA:
 2. A compound having the formula: 3.The compound cyclic O,O-2,2-dimethyltrimethyleneS,S''-(bicyclo(2.2.1)heptane-2,5-diyl) phosphorodithioate.